In recent telephone systems, a number of systems using a hybrid private branch exchange (PBX) including both functions of a conventional line switching function and a Voice over Internet Protocol (VoIP) function have been constructed. This telephone system has enabled accommodation of telephones and communication lines including various types of interfaces with different voice call characteristics such as analog telephones, digital telephones, internet protocol (IP) telephones, analog lines, digital lines, and IP lines. In this way, the combination of the connection between telephones and the connection between a telephone and a communication line has been diversified, which complicates the connection configurations of the telephone systems.
This has expanded the number of persons and time required to perform an operation for adjusting audio quality by a maintenance terminal and for checking voice call quality for all the connection paths by a telephone as a telephone system. Further, professional engineers having knowledge of VoIP are also required, which requires further improvement in maintenance performance.
Further, some connection paths may include a plurality of gain circuits for adjusting voice call level and a plurality of echo canceller circuits for cancelling echo. Thus, it is required to determine optimal circuits which are to be used to adjust voice call quality, which is a difficult operation that requires adjustment by a professional engineer.
As a means for solving these problems, Japanese Unexamined Patent Application Publication No. 2005-176071, titled “HYBRID TELEPHONE SYSTEM WITH VOICE QUALITY MANAGEMENT FUNCTION, AND HYBRID PBX USING THE SAME” (Patent literature 1) proposes installing an external device for automatically adjusting voice call quality in a telephone system. The external device includes a function of performing examination of voice quality for each of various communication paths/data accumulation function, a function of adjusting the voice quality for each of various communication paths/setting and updating functions/a function of controlling validation/invalidation of an echo canceller, thereby being able to automatically optimize setting of various parameters regarding call voice quality in each communication path in an echo canceller.